Many systems include flow sensors for sensing the flow rate of a fluid in one or more system conduits. For example, many forced air heating, ventilation, and air conditioning (HVAC) systems sense air flow for energy monitoring. In many of these systems, air flow is detected using a Pitot-static tube that extends into an air duct. This type of sensor, while generally reliable, do suffer certain drawbacks. For example, these types of sensors sense air flow in only a small region of the air duct, and thus cannot accurately measure non-uniform flow. These types of sensors additionally exhibit relatively low accuracy, and are sensitive to tube obstruction.
Hence, there is a need for an air flow sensor that can sense air flow over the entire cross section of an air flow duct, exhibits relatively high accuracy over time and with temperature variations, and/or is insensitive to obstruction by dust or other particulate. In addition to these needs, there is also a desire for an air flow sensor that is relatively inexpensive to install and relatively easy to calibrate. The present invention addresses one or more of these needs.